1. Field of the Invention
The present invention relates to an electrical swivel working machine including an electric motor as a driving source of an upper-part swivelling body of an electrical swivel working machine.
2. Description of the Related Art
Ordinarily, a lower-part traveling body includes a traveling body including a traveling mechanism used for traveling, and an upper-part swivelling body mounted on the lower-part traveling body. The upper-part swivelling body is operated, by a swivel mechanism. A working machine in which an electrical motor is used as a drive source of the swivel mechanism is called an “electrical swivel working machine” as in, for example, Japanese Laid-open Patent Publication No. 2010-150897.
A crawler may be used as a traveling mechanism of a lower-part traveling body of the working machine. When the crawler contacts the ground, the lower-part traveling body is supported by the ground through the crawler. While the working machine is stopped without traveling, the lower-part traveling body can stop on the ground without traveling relative to the ground by a friction force between the crawler and the ground. With this, if a swivelling reactive force acts on the lower-part travelling body when the upper-part swivelling body swivels on the lower-part traveling body, the lower-part traveling body can maintain the state where the lower-part traveling body is fixed to the ground.